Insulated homopolar generator



c. E. BERGER 2,103,931 INSULATED HOMOPOLAR GENERATOR Filed May 22, 1935 F151. 5 7 32 5 73 2 3 0 77 I I 3/ \fl 39 i 40 25 Patented Dec. 28, 1937 UNITED STATES PATENT OFFICE INSULATED HOMOPOLAR GENERATOR Application May 22, 1935, Serial No. 22,840

4 Claims.

This invention relates to generators, and inparticular, to homopolar generators for the production of low voltage currents, especially adapted for electro-plating purposes. In such generators the single inductor consists of the periphery of the rotor itself or a shell mounted directly thereon.

One object. of this invention is to insulate the active portion of the rotor in such generators from the drive shaft so as to prevent the leakage of current through the drive shaft and the remainder of the apparatus.

Another object is to provide an insulation for the active portion of the rotor from the drive shaft of the generator, and at the same time to provide a mounting adapted to hold the rotor tightly in connection with the drive shaft.

Referring to the drawing:

Figure 1 is a half vertical section through the homopolar generator of my invention, the lower half of the generator from the drive shaft to the floor being omitted.

Figure 2 is an enlarged fragmentary section of a modification.

Figure 3 is an enlarged fragmentary section of another modification.

Figure 4 is a vertical section, similar to Figure 1, but of a third modification.

Hitherto, in the design of homopolar generators for electro-plating and similar purposes, requiring a low voltage and high amperage current, no attempt has been made to insulate the inductor from its supporting shaft and bearings. If the bearings are mounted in the generator frame and not in separate insulated pedestals, the entire frame is connected to the generator output circuit. This renders the apparatus open to the danger of a short circuit or leakage of current, in case either the positive or negative bus bar line from the generator comes in contact with any metal object which might be connected to the generator frame. Another danger also arises from the possibility of a fault in the insulation of the high voltage motor driving the generator, or the high voltage field coils that are commonly used to excite the homopolar generator. In such event the short circuit resulting might impress a high voltage upon the low voltage bus bars to the electro-plating tanks, thus creating a hazard to the men working at the plating tanks.

These bus bars in electro-plating tanks are ordinarily unprotected because the low voltages ordinarily used to charge the anodes and cathodes are not dangerous to human life. The use of metal tanks and heating coils, however, frequently creates an electrical connection from the low voltage circuit to the pipe system and structural steel frame of the building. In such apparatus, as ordinarily constructed, insulation is provided only to the extent of preventing heavy low voltage currents from passing from tank to tank through pipes or supports, this insulation being generally inadequate to prevent the passage of high voltages as are used for motors and other purposes.

In loading and unloading the Work pieces in the electroplating tank of electroplating apparatus, the operators hands are commonly in contact With the work pieces while they are also in contact with the Work rod, which is in turn, connected with one of the generator terminals. t is for such electroplating work that the homopolar generator of this invention is especially adapted. Under such circumstances, therefore, it will be seen that the operator is in danger of injury if the low voltage generator circuit is not thoroughly protected from the high voltage supplied for the driving motor of the apparatus, or from the high voltage current which is commonly used to excite the generator fields. It is to avoid such accidents and consequent injury that the insulation of the present invention is provided.

Hitherto, underwriters or local ordinances have provided that the frames of motors shall be grounded by connecting them to the piping or frame-work of the building, this being connected to the earth. If, however, the homopolar generator frame or shaft is connected to the motor frame through the couplings, or through a common bed plate, a ground connection would thereby be provided in the low voltage circuit which might lead to loss of current or danger to the operator. While it is possible to isolate the generator by the use of insulating pads and couplings, the danger is not completely eliminated because there is always liability of someone thoughtlessly making an additional connection by means of an oil-retaining case over the couplings, uninsulated locating pins, panel-board supports and similar structures.

To solve this problem of preventing such leakages or dangers in the homopolar generator of my invention, I insulate the pulley-shaped armature of my generator from the shaft and thereby eliminate this danger at the very source. This insulation may be applied to insulate the armature from its support on the shaft, or else to insulate its rim from the web attached to the hub.

Referring to the drawing in detail, Figure 1 shows the homopolar generator of my invention with the insulation applied thereto. The generator itself is provided with a central frame section It, spaced apart from the end frame portions H. These frame members l8 and H constitute a stator which serves as pole pieces for the generator. Tapered roller bearings l3 and IE6! are supported upon the tapered sleeves it. Each pin i5 serves to prevent the tapered sleeve it from turning when tightening up the collar ll. The bearing cap I8 is supported by the cartridge housing E?) by means of screws 25. There is a running clearance between the collar H and the cap it sealed against loss of lubricant by felt rings in grooves in the cap H8. The cartridge housing [9 has similar grooves for felt rings to pre vent leakage between it and the sleeve it. The cartridge housing i9 is held between the shoulder 21 on the end frame H and the washer ring 22 by the bolts 23.

The end frames l l are roughly L-shape in half section, the axial portion 26 extending laterally within the ring of the pulley-shaped rotor, described later. The radial portions 25 are provided with annular grooves 26 on their inner faces for receiving the field coils 2?. The latter are mounted upon the insulation 2% and surrounded with sealing layers 29 on three sides. Above the field coils and extending inwardly from them are pads 39 through which pass the bolts 3! connecting the end frames H to the center section it of the generator frame. The generator center section it is provided with connecting peripheral portions 32 adapted to receive the threaded ends of the bolts 32, thereby connecting the outer frame portions ii to the central frame portion It The central frame portion ll? is provided with a series of bosses 34, on which are mounted insulation blocks 3%, these in turn, carrying the brush holder ring 36. The latter is preferably of copper and is secured to the central frame portion ill by means of machine screws 37, between the heads of which and the brush holder ring 36 are inserted suitable insulating washers. The brush holders 39 are mounted upon the brush holder rings 36 by the bolts 59, and are provided with brush-supporting arms d2 carrying the brushes 33. These brushes are yieldingly pressed into engagement with the collector rings 64.

The active portion of the generator rotor consists of a pulley-shaped member, generally designated 3'1, and having a half-sectional shape approximately like the letter I, the lower bar of the I representing the hub flange and the upper bar the peripheral flange. The bore of the rotor t? is outwardly fiared from its central transverse plane and in each of these flared portions, which are conical in shape, is provided an insulating member 49. Between this insulating member and the shaft l2 is provided an annular member 48, having a conical outer surface corresponding to the conical inner surface of the rotor bore. Two of these, annular members 18 are employed, being urged toward one another by the collars 5B, threaded onto the threaded portions 5! of the drive shaft [2. It will be obvious that when the collars 5d are tightened to force the annular members 48 inward, the insulating portions 49 will be forced against the inner surfaces of the hub bore of the rotor 57. In this manner there can be no passage of electricity from the armature or rotor ll to the drive shaft l2, and thence to the frame or other portions in contact with the drive shaft.

The rotor ll on its outer peripheral portion is provided with a plurality of radiating blades 5 3, which also serve as fan blades. These blades 55 are connected to the rotor 4? through the collector rings M by the screws 55. The rotation of the rotor l'l causes the blades 54 to create a suction, drawing air into the interior of the generator through the net-work 5t and discharging heated air through the apertures 5'? located between the outer frame members H and the central frame member ill. By this means the rotor 47 is cooled and prevented from being damaged by heat.

The insulation 59 may be of any suitable material, preferably consisting of mica or micanite (mica flakes with shellac or synthetic resin binders). Non-metal1ic keys or driving pins, or insulated metal keys or pins may also be used to prevent slipping. After such insulation is baked it may be machined accurately like metal. Synthetic resin materials; such as Bakelite, may also be used, or mica cones;

In the modified form of insulated rotor mounting shown in Figure 2, the rotor or armature ll is provided with a conical bore 53, having a taper corresponding to a conical enlargement 59 upon the drive shaft 2. The latter is provided with a single threaded portion 55 having a collar 50 threaded thereon, as in the previously described construction. Between the conical enlargement 59 and the conical bore 58 is arranged a flanged conical insulating member 63, serving the same purpose as the insulating members 49, described above. A washer 6! arranged between the flange of the insulating member til and the collar 58 serves to receive the thrust of the collar.

In the modified form of insulated armature or rotor shown in Figure 3, the armature or rotor is provided. with an enlarged bore 92, spaced apart from the drive shaft i2, thereby forming an air gap. Each face of the armature hub 63 is provided with a groove 64 of V-shape in cross section and of annular extent. In each of these grooves 64 is mounted an annular insulating member 65, of V-shape cross section. Engaging the inner surface of this insulating member 65 is a ring 66 having an annular fiange 57 of V-shape cross section. The drive shaft is provided with the usual threaded portions 55, upon which are mounted the threaded collars 5%. By turning the collars 5!] the rings 56 are forced into the annular grooves 54, thereby centering the rotor 47 with reference to the drive shaft 52, as well as creating the air space between its inner bore 62 and the drive shaft [2.

In the modified form of generator shown in Figure 4, the frame, generally designated 10, consists of a central frame portion (I connected to the outer frame members 12 and 13 by the bolts 74. The rotating part of the generator consists of an armature 15 mounted upon a drive shaft 15, which in turn, is journaled in anti-friction bearings H. The latter are mounted in the end plates l8 attached to each end of the machine and forming the casing thereof. One of the end plates 18 is provided with an axial bore 79 for the passage of the drive shaft l6, providing a lubrication space 80 to which lubricant is conveyed through the bore from the grease cup 82.

The rotor or armature 75 is shaped roughly in the form of a drum, with peripheral grooves 83, between which is a central portion 84 facing the central frame portion H, with an air space 8'! therebetween. Similar air gaps 87 exist between the outer armature portions 85 and 85 and the outer frame members 12 and 10, respectively. Another air gap is formed between the enlarged bore 88 of the armature l5 and the drive shaft 16. The central armature portion 84 is threaded, 75

as at 89, to receive the collector rings 90. The armature 15 in its end portions and 86 is provided with conical bores 9i. These are adapted to receive the thrust of corresponding conical rings 9-2 as impelled by the threaded rings 93 upon the threaded shaft portions 93a. Between the outer armature portion bores 9| and the conical rings 92 are arranged the insulating layers 94. The latter are in the form of conical shells. This insulating layer serves to insulate the shaft 16 from the armature l5, producing the current, thus preventing the danger of leakage at its very source. This insulation may be of the same material and constructed in the same manner as described for the types shown in Figures 1 to 3, inclusive.

The field coils 95 are mounted in the annular grooves 83 and supported upon brackets 96 carried by the end frame members 12 and 13. The collection of the current from the collector rings is made by means of bus bars 91 secured to opposite sides of the central frame member II by means of the screws 98, these bus bars 9'! being insulated in an appropriate manner by the insulating members 99. The inner ends of the bus bars 91 are provided with brush holders I00, carrying the brushes I0 I. The latter, in turn, engage the collector rings 90 in order to collect and transmit the current produced in the armature.

It will be understood that I desire to comprehend within my invention such modifications as come within the scope of the claims and the invention.

Having thus fully described my invention, what I claim as new and desire to secure by Letters Patent, is:

1. A homopolar generator comprising a drive shaft, a unitary rotor thereon including a hub having a central portion with an annularly flanged rim portion thereon, an outer stationary magnetic structure disposed adjacent the outer surface of said flanged rim portion, an inner stationary magnetic structure disposed adjacent the inner surface of said flanged rim portion, means for collecting the electricity from said rotor at opposite sides of said outer stationary magnetic structure, and means for preventing the conduction of electricity between said rotor and said shaft whereby to confine the passage of thecurrent generated from end to end of said flanged unitary rotor.

2. A homopolar generator comprising a drive shaft, a unitary rotor thereon including a hub having a central portion with an annularly flanged rim portion thereon, an outer stationary magnetic structure disposed adjacent the outer surface of said flanged rim portion, an inner stationary magnetic structure comprising stationary magnetic members disposed adjacent the inner surfaces of said flanged rotor portion on opposite sides of said central rotor portion, means for collecting the electricity from said rotor at opposite sides of said outer stationary magnetic structure, and means for preventing the conduction of electricity between said rotor and said shaft whereby to confine the passage of the current generated from end to end of said flanged unitary rotor.

3. A homopolar generator comprising a drive shaft, a unitary rotor thereon including a hub having a central portion with an annularly flanged rim portion thereon, an outer stationary magnetic structure disposed adjacent the outer surface of said flanged rim portion, an inner stationary magnetic structure disposed adjacent the inner surface of said flanged rim portion, means for collecting the electricity from said rotor at opposite sides of said outer stationary magnetic structure whereby to direct the cur rent generated from end to end of said flanged unitary rotor, and insulating structure disposed between said rotor and said shaft whereby to prevent the conduction of electricity through said shaft and to confine the conduction thereof from end to end of said rim portion.

4. A homopolar generator comprising a drive shaft, a unitary rotor thereon including a hub having a central portion with an annularly flanged rim portion thereon, an outer stationary magnetic structure disposed adjacent the outer surface of said flanged rim portion, an inner stationary magnetic structure disposed adjacent the inner surface of said flanged rim portion, means for collecting the electricity from said rotor at opposite sides of said outer stationary magnetic structure, and means for preventing the conduction of electricity between said rotor and said shaft whereby to confine the passage of the current generated from end to end of said flanged unitary rotor, said unitary rotor having its armature conducting means and its rotating magnetic means arranged in a single rotating structure.

CLARENCE E. BERGER. 

